Discontinuities in the surfaces of aerodynamic bodies, such as an aircraft wings and fuselage, can lead to boundary layer thickening, flow separation or breakdown of the airflow passing over them, resulting in lift reduction, and hence in a decreased fuel efficiency. Discontinuities may be features extending above or below the surface of the aerodynamic surface, or unfavourable curvatures which result in severe adverse pressure gradients.
Likewise, similar discontinuities on the surface of marine vehicles, such as the outer hulls of submarines, boats and ships, can result in increased resistance to motion of the vehicle as it passes through water, resulting in a lower achievable speed for a given fuel efficiency.
Where the discontinuities are generated by moveable control surfaces, for example on a rudder or the moveable slats at the leading edge of a wing, the fluid flow downstream of the discontinuity may become significantly disrupted, which at some fluid flow conditions, or rudder and slat angles, may additionally compromise the effectiveness of the moveable control surfaces.
Hence a means for preventing separation of flow or creating a modified boundary layer on fluid washed surfaces is highly desirable.